[sdiy] analog pitch shifter circuit?

[Richard Wentk]

At 16:35 04/01/2005, TIm Daugard wrote:
>From: "Paul Maddox"
>
> > Maybe its me but,
> > Couldn't you use good old fashioned hetrodyne techniques?
> > no digital stuff involved (no huge amounts of memory).
>
>I'm interested in the answers to this also . . .
>
>My 2 cents: The problem with hetroydyne methods is they are only good for pure
>sine. If you put a signal in with harmonics, and shift by 100 Hz, then the
>harmonics are also shifted exactly 100 Hz. This ruins the harmonic 
>relationship.

Indeed.

Pitch shifter != frequency shifter

With a pitch shifter/harmoniser you make an effort, no matter how 
unsuccessfully, to transpose the signal just as a sampler would. 
Mathematically you're multiplying all the component frequencies by a 
constant. With a frequency shifter you're *adding* a constant to all the 
component frequencies.

This has its uses, but it's not the same effect.

Richard